**5. Control parameters of the process of biogas**

The control of the anaerobic digesters is necessary to ensure a good operating of the digester. Since anaerobic digestion is a complex process implying several groups of microorganisms which are sensitive to several factors of operation, it is significant to be able to detect the non balance of the process at the beginning to take an action in time to prevent its failure. As with other biological processes, anaerobic digestion can be controlled by measuring the substrate convertion (COD or removed VS), the accumulation of intermediaries (VFA, pH, alkalinity, H2, CO), the formation of product (gas production rate, CH4, CO2).
